1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to disk drives that include a ramp used for the controlled loading of a head of a head stack assembly onto a disk of the disk drive.
2. Description of the Prior Art and Related Information
Ramp-loading disk drives utilize a ramp to transition a flying head off-of and back-onto a flying area above the surface of the rotating disk. The ramp typically interacts with a lift tab that supports the head. The disk is spun-up while the lift tab is on the ramp and the head is not in contact with the disk. Once the disk is rotating at a specific speed, the lift tab is moved down the ramp such that an air bearing is developed between the head and the disk. The head may then move free of the ramp. Before the disk is spun-down, the lift tab is moved onto the ramp such that the head is moved away from the disk.
One method of increasing the storage capacity of disk drives is to store data more densely on each disk. One of the consequences of storing data more densely on a disk, however, is that the head must be correspondingly decreased in size and must fly closer to the recording surface of the disk. Another method of increasing the storage capacity is to manufacture disk drives with a greater number of stacked platters (i.e. individual disks). The latter method has led to relatively tall disk stacks, for example, three or more individual disks, each of which has two recording surfaces. However, it has proven difficult to precisely align each of the ramps to the respective recording surfaces of each disk in a tall disk stack.
The loading of heads of the head stack assembly (HSA) onto disks of a disk stack is typically accomplished utilizing sloped ramps that are made out of stainless steel. The slope of the sloped ramps is designed to load each head onto each disk with a low occurrence rate of head disk interactions. Head disk interactions, such as head slaps, may increase the risk of head and disk damage. Unfortunately, head disk interactions, such as head slaps, still occur and with time, and after many uses, the slope of the sloped ramps may change such that they may fail to adequately control the load velocity of the heads onto the disks properly. This failure to control the load velocity leads to an increased rate of head slaps when heads of the HSA are loaded onto disks of the disk stack. In addition, current sloped ramps create a certain amount of lateral motion between the head and the disk when the head is loaded onto the disk, which increases the risk of head and disk damage due to head disk interactions.